The present invention relates to a piston member, to a pump head, to a high-pressure pump for pumping fluid, to a sample separation apparatus, and to a method of manufacturing a piston member for a high-pressure pump for pumping fluid in a sample separation apparatus.
In a sample separation device based on the principle of liquid chromatography, a fluidic sample to be separated is injected in a mobile phase (such as a solvent composition), wherein the mixture may be pumped through conduits and a column comprising a material (stationary phase) which is capable of separating different components of the fluidic sample. Such a material, so-called beads which may comprise silica gel, may be filled into a column tube which may be connected to other elements (like a sampling unit, a flow cell, containers including sample and/or buffers) by conduits.
For pumping the mobile phase to the sample separation device, a pump may be implemented in which a piston reciprocates within a pumping chamber to thereby displace the mobile phase. For injecting a fluidic sample into the mobile phase, another metering pump may be implemented in a sample injector of the sample separation device to thereby inject the fluidic sample into the mobile phase.
U.S. Pat. No. 4,036,232 discloses an aspiration unit which will afford a uniform suction level for aspirating fluids from body cavities. The unit is composed of a double piston member, a first head of which is in sealing engagement with a syringe barrel and the second head of which is oppositely disposed and is contained in a telescoping member which is also receivable in the syringe barrel. Upon movement of the telescoping member outwardly from the syringe barrel, a vacuum will be created in the telescoping member as well as in that portion of the barrel member between the first piston member and the nozzle which is closed from atmosphere by means of a valve member. Upon insertion of a flexible tube into a body cavity and opening of the valve member, fluid will be aspirated into the syringe barrel by means of the partial vacuum created in the syringe barrel and in the telescoping member. A clamp means is provided to hold the telescoping member in the vacuum creating condition while the tubular member is inserted into a body cavity. The aspirating device is operable with one hand and is disposable.
U.S. Pat. No. 4,939,943 discloses a sample injector for a liquid chromatograph which comprises a high pressure syringe unit, a sample intake unit having a needle which can be introduced into a sample container as well as a seat, and a 6/2-way valve. The high pressure syringe unit is designed as a piston pump with a pump head and a piston which is driven by a motor via a drive mechanism. Pressurized liquid from a solvent delivery system can enter the pump head through an inlet port and flow along the piston to an outlet port. When sample is to be injected into a chromatographic column, the 6/2-way valve is first switched into the position depicted by dotted lines, the needle is introduced into the container and the piston is retracted by a corresponding distance. Thereafter, the valve is switched back to its original position so that solvent delivered from the solvent delivery system can transport the sample to the column. Since the solvent flushes the entire syringe unit, it is ensured that no sample residues remain in the syringe unit which would otherwise impair the chromatographic measuring process.
U.S. Pat. No. 6,984,222 discloses a plunger system for use in an injector-actuated syringe which includes a dynamic wedge seal which improves the sealing engagement between the plunger cover and syringe barrel, and flexible capture members extending from the rear surface of the plunger which permit the engagement and disengagement of the plunger from the injector drive means at any plunger position within the syringe. Further, the plunger systems include a contrast saving tip which expels the injection liquid from the syringe tip.
However, when the pressure values according to which fluid is pumped by the pump become larger and larger, a mechanically stable pump is required which is at the same time reliably sealed.